Compression ignition internal combustion engines



June 28, 1966 c. CLEMENTS ETAL 3,257,994

COMPRESSION IGNITION INTERNAL COMBUSTION ENGINES Filed June 1.7, 1964 5 Sheets-Sheet 1 June 28, 1966 c. CLEMENTS ETAL 3,257,994

COMPRESSION IGNITION INTERNAL COMBUSTION ENGINES Filed June 1.7, 1964 5 Sheets-Sheet 2 42%; at 4 ya.

June 28, 1966 c. CLEMENTS ETAL 3,257,994

COMPRESSION IGNITION INTERNAL COMBUSTION ENGINES Filed June 1.7, 1964 3 Sheets-Sheet 3 United States Patent 3,257,994 COMPRESSION IGNITION INTERNAL COMBUSTION ENGINES Colin Clements, Solihull, and Douglas Leslie Sutton, Castle Bromwich, England, assignors to The Rover Company Limited, Solihull, England, a British company Filed June 17, 1964, Ser. No. 375,728 Claims priority, application Great Britain, June 20, 1963, 24,527/ 63 9 Claims. (Cl. 123-32) This invention relates to liquid fuel injection compression ignition internal combustion engines of the kind .in which, during the compression stroke of the piston,

at least the greater part of the air charge in the cylinder is forced through a transfer passage or passages into a pre-combustion chamber into which the fuel is injected. The invention relates chiefly, though not solely, to those engines of this kind in which the air charge enters the chamber tangentially through the transfer passage and is consequently in a state of bodily rotation when the fuel is injected into it, such chambers being known as swirl chambers.

In engines of the kind described above various proposals have been made for the provision of an auxiliary transfer passage or passages in addition to the main passage, directed either into the pre-combustion chamber or into an auxiliary recess into which the fuel is injected, the purpose of such auxiliary passages being to assist in creating turbulence or to assist in carrying the fuel into the main pre-combustion chamber.

It is an aim of the invention to achieve a still further improvement in the provision of such auxiliary transfer passages, and in particular to reduce the delay period in the combustion process and to obtain smooth and quiet running of the engine. A particular aim is to provide smooth and quiet running during the first few moments of running after starting from cold; rough and noisy starting is a noticeable feature of many known engines, even those which are quiet when hot.

A further aim of the invention is to obtain an improvement in combustion in the chamber such as will assist in enabling the engine to be run on any of a wide range of fuels, including those of relatively low cetane number.

According to the invention there is now proposed an internal combustion engine of the liquid fuel injection compression-ignition type in which, during the compression stroke of the piston, at least the greater part of the air charge in the cylinder is forced through a main transfer passage or passages into a pre-combustion chamber into which the fuel is injected, and in which at least one auxiliary passage connects the cylinder with the combustion chamber in addition to the main passage or passages, distinguished by the feature that the auxiliary passage, or each such passage, opens into the combustion chamber in a direction such as to produce a current of air from the cylinder in a direction transverse to the stream of fuel which is directed within the pre-combustion chamber towards that region of the chamber wall in the neighbourhood of the or each auxiliary passage.

We have found that this provision for a flow of air from an auxiliary passage or passages reduces the delay period of the combustion process and produces smoother and quieter running than in known engines, especially during the first few moments on starting from cold.

The invention is preferably applied to a swirl type of chamber, in which the main transfer passage or each such passage enters the chamber tangentially and the fuel is injected into the rotating air charge in the chamber. It is particularly applicable to that kind in which the fuel is at least predominantly injected tangentially in a downstream direction and in which a portion of the chamber, including the point at which the main transfer passage is disposed, is formed in a plug having a limited heatconducting connection with the remainder of the engine. The or each auxiliary transfer passage can be formed in this hot plug or by an enlarged portion of the clearance between the plug and the remainder of the engine, and the or each passage communicates with the interior of the chamber through one or more holes or notches in the wall of the plug.

According to a still further feature of the invention the auxiliary transfer passage is used in conjunction with an injector that provides an auxiliary spray of fuel at an angle to the main spray and towards the wall of the chamber lying on the downstream side of the injector but upstream of the auxiliary transfer passage or passages.

The invention will now be further described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a vertical section through the upper part of a portion of an internal combustion engine to which the invention is applied;

FIGURE 2 is a vertical section, in the same plane as FIGURE 1, on a much larger scale showing the hot plug that forms a part of the pre-combustion chamber of the engine; this section is on the line 22 in FIGURE 3;

FIGURE 3 is a ventioal section through the hot plug alone, this section being on the line 33 in FIGURE 4, and the plane of the section being perpendicular to that of the section of FIGURE 2;

FIGURE 4 is a plan view of the hot plug;

FIGURE 5 is a view similar to FIGURE 1, showing an alternative form of chamber, especially suited for running on a wide range of fuels; and

FIGURE 6 is a fragmentary sectional view taken along the lines indicated by 66 in FIGURE 5.

Referring first to FIGURE 1 the engine is basically of a known kind in which a piston 1 moving vertically in a cylinder 2 acts, on its upward compression stroke to force the greater part of the air charge in the cylinder through a transfer passage 3 which directs the air tangentially into a pre-combustion chamber 4 of modified spherical or spheroidal shape. Into the resultant rotating air charge in the chamber 4 (known as a swirl type of pre-combustion chamber) a quantity of fuel is injected tangentially in a downstream direction from an injector 5.

The transfer passage 3 and the lower half of the chamber 4 are formed in a separate member 6 of generally cylindrical shape, made of a heat-resisting metal alloy and disposed, with its axis vertical, in a suitable recess in the cylinder head 7 of the engine; in other arrangements the chamber could be formed in the cylinder block of the engine instead of the cylinder head. It would also be possible for there to be more than one transfer passage 3, for example there could be two side by side.

The member 6 is known as a hot plug and has limited heat-conducting contact with the cylinder head 7 or other engine part in which it is mounted. A flange 8 around the lower end of the plug is clamped against a shoulder 9 in the cylinder head 7 when the cylinder head is secured to the cylinder block, and this holds the plug in place without the outer cylindrical wall of the plug nor its upper end face coming into direct metallic contact with the adjacent surfaces of the cylinder head. There is in fact avery small clearance, not visible in the drawings, at these points. A pin 10 in the cylinder head is engaged by a notch 11 (FIGURE 4) in the flange 8 to locate the plug 6 in its correct angular position.

In the modification according to the present invention a portion of the outer cylindrical surface of the plug 6 is ground away or otherwise removed over a region of the plug opposite that side of the plug to which the transfer passage 3 directs the incoming air charge. The surface could be made flat, i.e. it would be defined by a chordal plane, but in the preferred embodiment shown it is simply ground to a larger radius than the remainder of the cylindrical surface, as indicated by the broken line at 15 in FIGURE 4. The result is that, when the plug is in place in the cylinder head, there is defined a wide very thin passage 16 of arcuate profile, extending upwards parallel to the axis of the plug. At the lower end of the passage a portion of the flange 8 is cut away at 17 to provide communication with the cylinder 2.

At its upper end the passage 16 stops short of the top face of the plug 6 and communicates with the recess in the interior of the plug by means of two laterally spaced-radially extending holes 18.

In the example shown the interior of the recess, upstream of the upper end of the main transfer passage, carries a series of closely spaced projections 19 designed to upset the smooth flow of the rotating air charge and to ensure its thorough mixing with the fuel, these projections being the subject of our Patent No. 901,981. Instead of projections, depressions could be used with much the same effect. It will be seen that the holes 18 of the present invention open into the chamber just above the upper row of projections 19.

The main body of fuel is injected into the rotating air charge by the injector in a tangential downstream direction, as indicated at 20 in FIGURE 1. This main body is directed substantially towards that portion of the charge which is simultaneously being subjected to the blast of air that is entering the chamber horizontally, i.e. in a direction substantially transverse to the path of the main body 20 of fuel.

A further feature of the invention is that, in addition to the main body 20 of fuel directed downstream towards the region of the upper edge of the recess in the plug 6, a minor portion 21 of the fuel is simultaneously directed towards a point in the wall of the chamber upstream of this region. This is achieved by the provision of an auxiliary nozzle in the injector 5, and is distinct from the known socalled Pintaux arrangement by which a minor portion 22 of the fuel is directed radially or slightly upstream under starting or light-load conditions.

During operation of the pre-combustion chamber described, the flow of air through the main transfer passage 3 on the compression stroke of the piston 1 is accompanied by a flow through the auxiliary transfer passage 17, 16, 18, so that when the fuel is injected into the rotating air charge in the chamber the droplets of fuel are met by a transverse flow of air from the holes 18. The effect of this is found to be that the correct air-fuel mixture for combustion is obtained earlier in the combustion cycle than was previously possible and the delay period is thus reduced. There is a more controlled rate of pressure rise and consequently smoother running of the engine. A still further improvement is achieved by the auxiliary spray of fuel droplets 21 towards a point in the wall of the chamber upstream of the holes 18.

The reduction in the delay period and the smoothness of running as compared with known engines are particularly apparent during starting from cold; this is believed to be because, as combustion proceeds, the hot gases of combustion stream back down the passage 18, 16, 17 and heat it up rapidly within the first few revolutions of the engine. The adjacent surfaces of the plug and of the cylinder head very quickly reach their working temperatures, and the shape of the passage 16, with a very large surface area in relation to its cross-sectional area, ensures that the heat imparted to these surfaces by the hot gases of combustion is effectively and rapidly transmitted to the rising current of air on the next compression stroke. Consequently within a very short time from starting, the blast of air emerging from the holes 18 at each compression stroke is at a very high temperature.

Although we have shown the holes 18 as extending through the wall of the plug a short way below its upper edge they could, in a modification, be in the form of notches in its upper edge. It will be understood that there could be only one hole, or more than two. Likewise the passage 16 itself could if desired be replaced by two or more passages.

Turning now to FIGURE 5, the same reference numerals have been used as in FIGURE 1, where applicable. There is a piston 1 moving vertically in a cylinder 2 and forcing the air on the compression stroke through a transfer passage into a swirl type of pre-combustion chamber 4, into which fuel is injected by an injector 5 and the lower half of the chamber is formed by a hot plug. However the plug, shown at 6 is of modified external shape and the upper half of the chamber, instead of being formed directly in the cylinder head 7, is formed by a shell 23 of heat-resisting sheet metal; this feature is the subject of our United Kingdom Letters Patent No. 903,- 361. An outwardly directed flange around the lower edge of this shell is welded to a flange 24 at the upper end of the hot plug 6'.

The inside of the shell 23 and of the recess in the plug 6 may be coated with heat-resisting material such as a ceramic in order to reduce thermal shock and/ or attack byproducts of combustion, such as those of leaded fuels.

The plug 6 is not mounted directly in the cylinder head 7 but instead there is a cylindrical sleeve 25 of which the upper end is welded to the flange 24 on the upper end of the plug 6, whilst the lower end of the sleeve has an outwardly directed flange 8 serving the function of the flange 8 of the earlier embodiment, i.e. to hold the plug in place by location against a shoulder in the cylinder head when the cylinder head is placed in position; in this case it holds the whole chamber comprising the plug 6 and the shell 23 in a position spaced away from the recess in the cylinder head 7 that receives it.

There is a small clearance between the interior of the sleeve 25 and the outside of the plug 6 and a similar clearance between the outside of the sleeve and the wall of the cylinder head. The plug 6 is thus doubly insulated from the cylinder head and can attain even higher temperatures than the plug 6 of FIGURE 1.

The auxiliary transfer passage is formed just as in the earlier arrangement by relieving locally the outside cylindrical surface of the hot plug to form a thin vertical space 16'. For example, where the clearance between the sleeve and the plug is ten thousandths of an inch around the remainder of the periphery of the plug, it is made double this in the region of the left-hand side of the plug in FIGURE 5.

In place of the two holes 18 of FIGURES 1 to 4 the example of FIGURE 5 uses four holes 18, spaced over an arc of about ninety degrees (as viewed from above).

The behaviour of the embodiment of FIGURE 5 is the same as that of FIGURES 1 to 4. However the emphasis in FIGURE 5 is on high temperature, which enables the engine to be run on a wide range of fuels, including those of relatively low cetane number. The auxiliary transfer passage 16' is substantially hotter than the passage 16 because it is between two walls both of which are thermally insulated from the cylinder head 7. A heater plug 26 is used to assist starting.

A further modification that may be applied to the embodiment of FIGURE 5 is shown in FIGURE 6, instead of a single auxiliary spray 21 as shown in FIGURE 1 towards a point in the wall upstream of the auxiliary transfer passage, there may be two such sprays 21' and 21", diverging at a mutual included angle of up to and inclined in equal and opposite direction to the plane of the section shown in FIGURE 5. The major part of the fuel is still fed to the main spray 20, but these two auxiliary sprays could between them account for between twenty and fifty percent of the total fuel delivery.

We claim:

1. An internal combustion engine comprising a cylinder, a piston reciprocable in said cylinder, structure defining a cavity, a plug disposed in and occupying part of said cavity, a recess in said plug disposed so that said recess co-operates with said cavity to define a pre-combustion chamber of generally spheroidal shape, said plug being connected to said structure by means having limited heat-conducting contact therewith, said plug having formed therein a first transfer passage forming a communicating path between said cylinder and said chamber, said first transfer passage being directed tangentially with respect to said chamber so as to direct a stream of air from said cylinder into said chamber tangentially to set up a body of air in said chamber rotating about an axis, there being clearance between said plug and said cavity defining a second transfer passage, said second passage being of smaller cross sectional area than said first passage and communicating at one end with said cylinder, a fuel-injection nozzle, said nozzle being mounted in said structure and orientated to direct a stream of fuel across a portion of said chamber towards 'a region of the wall of said recess, in a direction downstream with respect to the rotating body of air within the chamber, and the other end of said second transfer passage communicating with said recess adjacent said region and being disposed to direct a current of air from said cylinder into said chamber in a direction transverse to the direction of said stream of fuel.

2. In an internal combustion engine a cylinder, a piston reciprocable in said cylinder, a structure defining a cavity adjacent said cylinder, a cylindrical plug disposed with a portion of said cavity and having a recess therein which co-operates with the remainder of said cavity to define a pro-combustion chamber of generally spheroidal shape, said plug having a predominantly cylindrical external shape and havingits external cylindrical wall close to but spaced from the adjacent cylindrical internal wall of the cavity, means locating said plug in said cavity in restricted heat-conducting relationship, there being a first transfer passage formed in said plug and extending therethrough in a direction tangential withrespect to said chamber, one end of said passage communicating with said chamber and the other with said cylinder, a fuel injection nozzle, said nozzle being mounted in said structure and entering said chamber and being disposed to direct a stream of fuel across said chamber towards a region of the wall of said recess, a portion of the cylindrical surface of the wall of said plug being at least partially flattened locally to define between said wall and the internal wall of said cavity a second transfer passage, said second passage extending parallel to the axis of said plug and forming a communication between said cylinder and said recess, and said second passage being furthermore of smaller cross-sectional area than said first passage and of cross-sectional area which is small in relation to the surface area of the walls which define it.

3. In an internal combustion engine, an assembly of parts as set forth in claim 2, wherein said second transfer passage opens into said recess in the region towards which a stream of fuel is directed by said nozzle, and is disposed to direct a current of air from said cylinder across said chamber in a direction transverse to the direction of the stream of fuel.

4. In an internal combustion engine, a cylinder, a piston reciprocable in said cylinder, structure adjacent said cylinder defining a cavity open at one end, a plug disposed in the open end of the cavity and having therein being mounted in said structure and disposed to direct fuel across said chamber towards a region of the Wall of said recess, a first transfer passage being formed in said plug and forming a communication between said cylinder and said chamber, and the external cylindrical surface of said plug being at least partially flattened 1ocally to define, between said plug and sleeve, a second transfer passage of smaller cross-sectional area than the first passage, one end of said second passage opening into the cylinder whilst the other end of said second passage opens into said recess in said region and is disposed to direct a current of air from the cylinder into the chamber in a direction transverse to the direction of the stream of fuel.

5. In an internal combustion engine, an assembly of parts as set forth in claim 4-, comprising further a sheet metal shell of generally part-spherical shape, said shell lying within said cavity and forming a lining to said chamber, cooperating with said recess.

6. A plug for use in an internal combustion engine of the fuel-injection compression ignition type in which, during the compression stroke, of the piston, at least the greater part of the air charge in the cylinder is forced into a swirl type of pre-combustion chamber and set therein into a state of organised rotation, whilst fuel is injected into the rotating air charge, said plug comprising a generally circular cylindrical body of heat resisting metal, having formed in one end face a recess designed to form a portion of a pre-combustion chamber, and having formed therein a first transfer passage extending between the other end face and the interior of said recess, said transfer passage being inclined to the axis of the plug, and the external cylindrical surface of said plug being locally modified by at least partially flattening an axially extending portion thereof such that, when said plug is received in a closely fitting cylindrical cavity, the cooperation of the cavity with said locally modified portion defines a second transfer passage.

7. An internal combustion engine of the liquid fuel injection compression ignition type in which, during the compression stroke of the piston, at least the greater part of the air charge in the cylinder is forced into a precombustion chamber into which the fuel is injected, said engine comprising a cylinder, a piston reciprocable in said cylinder, a body having formed therein a cavity of basically spheroidal shape forming a swirl-type precombustion chamber, a structure defining a first transfer passage extending between said chamber and said cylinder, said passage being directed to meet said cavity in a substantially tangential direction to produce rotation of the air charge in said cavity about an axis perpendicular to said passage, a fuel injection nozzle, said nozzle being disposed in a wall of said chamber and orientated to direct a stream of fuel tangentially downstream into the rotating air charge in a direction across a portion of said chamber towards a region of the wall thereof displaced from said nozzle, and structure defining a second transfer passage extending between said chamber and said cylinder, said second transfer passage being of substantially smaller cross-sectional area than said first transfer passage and opening into the wall of said chamber adjacent to said region towards which the stream of fuel is directed a recess facing towards the closed end of said cavity 7 by said nozzle and being orientated to direct a stream of air into said chamber in a direction transverse to the direction of the stream of fuel.

8. An internal combustion engine of the liquid fuel injection compression ignition type in which, during the compression stroke of the piston, at least the greater part of the air charge in the cylinder is forced into a precombustion chamber into which the fuel is injected, said engine comprising a cylinder, a piston reciprocable in said cylinder, a cooled engine component having formed therein a first recess, a cylindrical plug, said plug being mounted in said body and having limited heat-conducting contact therewith and having formed therein a secnd recess complementary to said first recess whereby said recesses define together a cavity of generally spheroidal shape forming a pre-combustion chamber, structure within said plug defining a main transfer passage forming a communication between said cylinder and said chamber, said main passage being directed to meet said cavity in a substantially tangential direction to produce rotation of the air charge in said cavity about an axis perpendicular to said passage, a fuel-injection nozzle, said nozzle being mounted in said body in a wall of said first recess and disposed to direct a stream of fuel tangentially downstream into the rotating air charge in a direction across said chamber towards a region of the wall of said second recess, structure in said plug and defining an opening communicating with said chamber adjacent said region, and the exterior of said plug and the interior of said engine component being locally spaced apart to define between them an auxiliary transfer passage communicating at one end with said opening and at its other end with said cylinder, said auxiliary transfer passage being of substantially smaller cross-sectional area than said main transfer passage.

9. In an internal combustion engine a cylinder, a piston reciprocable in said cylinder, a structure defining a cavity adjacent said cylinder, a cylindrical plug disposed with a portion of said cavity and having a recess therein which co-operates with the remainder of said cavity to define a pre-cornbustion chamber of generally spheroidal shape, said plug having a predominantly cylindrical external shape and having its external cylindrical wall close to but spaced from the adjacent cylindrical internal wall of the cavity, means locating said plug in said cavity in restricted heat-conducting relationship, there being a firsttransfer passage formed in said plug and extending therethrough in a direction tangential with respect to said chamber, one end of said passage communicating with said chamber and the other with said cylinder, a fuel injection nozzle, said nozzle being mounted in said structure and entering said chamber and being disposed to direct a first stream of fuel across said chamber towards a region of the Wall of said recess, said nozzle comprising additional means adapted to direct a second stream of fuel, smaller than said first stream, in a direction towards the wall of said chamber which is disposed between said nozzle and said first-mentioned region, a portion of the cylindrical surface of the Wall of said plug being at least partially flattened locally to define between said wall and the internal wall of said cavity a second transfer passage, said second passage extending parallel to the axis of said plug and forming a communication between said cylinder and said recess, and said second passage being furthermore of smaller crosssectional area than said first passage and of cross-sectional area which is small in relation to the surface area of the walls which define it, said second transfer passage opening into said recess in the region towards which a stream of fuel is directed by said nozzle, and being disposed to direct a current of air from said cylinder across said chamber in a direction transverse to the direction of said first stream of fuel.

References Cited by the Examiner UNITED STATES PATENTS 2,058,827 10/1936 Ricardo 12332.9 2,223,090 11/1940 Boxan 123-33 2,925,070 2/1960 Meurer 123--32.91 2,970,584 2/1961 Wunsche et al 123-3291 3,168,079 2/1965 Henderson 12332.91

FOREIGN PATENTS 1,097,913 2/ 1955 France.

MARK M. NEWMAN, Primary Examiner.

RICHARD B. WILKINSON, Examiner. 

1. AN INTERNAL COMBUSTION ENGINE COMPRISING A CYLINDER, A PISTON RECIPROCABLE IN SAID CYLINDER, STRUCTURE DEFINING A CAVITY, A PLUG DISPOSED IN AND OCCUPYING PART OF SAID CAVITY, A RECESS IN SAID PLUG DISPOSED SO THAT SAID RECESS CO-OPERATES WITH SAID CAVITY TO DEFINE A PRE-COMBUSTION CHAMBER OF GENERALLY SPHEROIDAL SHAPE, SAID PLUG BEING CONNECTED TO SAID STRUCTURE BY MEANS HAVING LIMITED HEAT-CONDUCTING CONTACT THEREWITH, SAID PLUG HAVING FORMED THEREIN A FIRST TRANSFER PASSAGE FORMING A COMMUNICATING PATH BETWEEN SAID CYLINDER AND SAID CHAMBER, SAID FIRST TRANSFER PASSAGE BEING DIRECTED TANGENTIALLY WITH RESPECT TO SAID CHAMBER SO AS TO DIRECT A STREAM OF AIR FROM SAID CYLINDER INTO SAID CHAMBER TANGENTIALLY TO SET UP A BODY OF AIR IN SAID CHAMBER ROTATING ABOUT AN AXIS, THERE BEING CLEARANCE BETWEEN SAID PLUG AND SAID CAVITY DEFINING A SECOND TRANSFER PASSAGE, SAID SECOND PASSAGE BEING OF SMALLER CROSS SECTIONAL AREA THAN SAID FIRST PASSAGE AND COMMUNICATING AT ONE END WITH SAID CYLINDER, A FUEL-INJECTION NOZZLE, SAID NOZZLE BEING MOUNTED IN SAID STRUCTURE AND ORIENTATED TO DIRECT A STREAM OF FUEL ACROSS A PORTION OF SAID CHAMBER TOWARDS A REGION OF THE WALL OF SAID RECESS, IN A DIRECTION DOWNSTREAM WITH RESPECT TO THE ROTATING BODY OF AIR WITHIN THE CHAMBER, AND THE OTHER END OF SAID SECOND TRANSFER PASSAGE COMMUNICATING WITH SAID RECESS ADJACENT SAID REGION AND BEING DISPOSED TO DIRECT A CURRENT OF AIR FROM SAID CYLINDER INTO SAID CHAMBER IN A DIRECTION TRANSVERSE TO THE DIRECTION OF SAID STREAM OF FUEL. 